[klondike98]

If you don't care about preserving the artwork you could try using some of the derusting products out there such as Evaporust or Metal Rescue to take off the rust and then repaint to protect the metal. Its also possible those products may not affect the existing paint but I'm not sure about that. Something like naval jelly will take the existing paint off along with the rust. Just some ideas...others will surely chime in...